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The objective of the study was to determine the effects of molecular sizes of amylose (AM) and starch granules on the mechanical properties of thermoplastic starch (TPS) blend films. Leached amylose solution from cassava (CS_ AM) and mung bean (MB_AM), and two forms of amylopectin (AP) (granular; g and non-granular; ng) of waxy cassava (WxCS) starch were used. Four types of film matrices were fabricated and all TPS blend films contained same amount of AM and glycerol. Results displayed that molecular weight profiles of starch films and presence of granule remnants significantly controlled the film matrix formation, types of crystal formation, and percent of relative crystallinity (%RC) (p < 0.05). Tensile property of TPS films was controlled by %RC and presence of granule remnants. Percent elongation at break (%Eb) of TPS films increased when the films had a large range of molecular weight distribution (from 5.5 × 107 g/mol to 0.4 × 105 g/mol) and contained a high weight fraction (~58%) of starch molecules with Mw~0.4 × 105 g/mol. 相似文献
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Reducing water absorption in compostable starch-based plastics 总被引:1,自引:0,他引:1
M. Gspr Zs. Benk G. Dogossy K. Rczey T. Czigny 《Polymer Degradation and Stability》2005,90(3):563-569
To improve the mechanical and physical properties of corn starch-based bioplastics the addition of natural polymers was investigated. Thermoplastic starch (TPS) was made of 70 g corn starch and 30 g glycerol. To this mixture 10–10 g of cellulose, hemicellulose and zein (protein) were added. Mechanical strength, water absorption and enzymatic degradation of composite materials were measured. Unfilled TPS and 10 w/w% polycaprolactone filled TPS were used as controls in the experiments. All the samples were biodegradable by enzymes. The tensile strength of unfilled and biopolymer filled TPS samples were significantly higher than that of the polycaprolactone filled one. Hemicellulose and zein composites had the best mechanical strength (10.4 and 11.5 MPa). Water uptake of each sample was measured using five different relative humidities. There were slight differences in water uptake of polycaprolactone, hemicellulose and zein filled TPS, however unfilled and cellulose filled samples absorbed more moisture than the polycaprolactone control in all the relative humidities used. 相似文献
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Recently, it is found that telegraph equation is more suitable than ordinary diffusion equation in modelling reaction diffusion for such branches of sciences. In this article, we propose a numerical scheme to solve the one‐dimensional hyperbolic telegraph equation using collocation points and approximating the solution using thin plate splines radial basis function. The scheme works in a similar fashion as finite difference methods. The results of numerical experiments are presented, and are compared with analytical solutions to confirm the good accuracy of the presented scheme. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008 相似文献
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Eliangela de Morais Teixeira Alessandra Luzia Da Róz Antonio José Felix de Carvalho Antonio Aprigio da Silva Curvelo 《Macromolecular Symposia》2005,229(1):266-275
Summary: Thermoplastic starches (TPS) based on cassava starch have been produced by extrusion at 120 °C, using glycerol as plasticizer. Three forms of cassava starch were employed, viz: cassava root (CR), cassava bagasse (CB) and purified cassava starch (PCS). The main differences between these are the presence of sugars and a few fibres in CR and high fibre concentration in CB. Conditions of processing and characteristics such as amylose and fibre content, crystallinity, water absorption and mechanical behaviour in the tension x deformation test were evaluated. The results demonstrated that the PCS and CR had amylose contents consistent with literature values (14–18%) and that CB is a material constituted mainly by amylopectin. It was found that fibres in high proportions (as in the bagasse) can confer reinforcement properties and are thus able to generate natural composites of TPS with cellulose fibre. The sugars naturally found in the root reduce the elongation of the TPS under tension. The PCS and CR TPS were stable with respect to indices of crystallinity after processing; and during a period of 90 d in a relative humidity of 53%, while the CB TPS tended to vary its crystallinity, probably because its amylose chain had low degree of polymerization. 相似文献